Current efforts to produce gratings in optical telecommunication fibers can suffer from a number of undesirable manufacturing choices including: removal of the fiber coating; use of infrared radiation requiring costly lasers (an IR femtosecond pulse laser system can easily exceed $200K), limiting the types of structures that may be formed; fiber features which are too strongly reflective to be suitable for use in the multiplexing of serial sensors, and so forth.
For example, removal of the fiber coating and recoating, necessitated by the opacity of the coating when excimer laser wavelengths are used, may cause the fiber strength to degrade and also increase the time consumption and therefore the cost of fiber Bragg grating (FBG) fabrication. To solve this coating removal induced problem, FBGs may also be fabricated during the fiber fabrication on a fiber draw tower. The bare glass fiber is exposed to excimer laser induced interference fringes before the fiber coating is applied. This method is effective but requires significant equipment capital investment and the tower operation and maintenance is also costly. In addition, the fiber drawing speed is usually high, typically a number of meters per second, so the control on the grating characteristics and the fabrication yield may be limited.
Accordingly it would be an advance in the art to provide new and useful optical fiber sensors and methods for their production.